Methanol-to-olefins (MTO) processes can produce olefin-containing streams which contain ethylene and trace levels of contaminants. The olefin-containing streams obtained from MTO processes can contain olefins other than ethylene, and the contaminants can include sulfur-containing compounds, diolefins, hydrogen, carbon monoxide, and paraffins. These other olefins and/or contaminants can prevent direct use of the olefin-containing streams in polyethylene polymerization processes without purification of the ethylene in the olefin-containing streams, since the desired olefin to be polymerized is ethylene and the contaminants can poison the catalysts used in ethylene polymerization. The olefin-containing streams obtained from MTO processes can also contain polar contaminants such as oxygenated hydrocarbons (ethers, esters, acids, carbonyls) which can deactivate certain polyethylene polymerization catalysts (e.g., Ziegler-Natta and metallocene catalysts). There is an ongoing need for purification techniques which convert olefin-containing streams obtained from MTO processes to streams suitable for feeding to ethylene polymerization processes.